Automatic stoker



Jly 10, 1934. o. I AJolE- AUTOMATIC STOKER Filed Sept. 18, 1931 Fig. f

INVENTOR v/Ya q/'a/' BY LAI/@mg ATTORNEY Patented July I, 1934 UNITED STATES PATENT ori-ICE AUTOMATIC STOKER Ovlla Lajoie, Lowell, Mass. Application september 1s, 1931, serial No. 563.493

4 Claims. '(Cl. 126-146) tem over other devices of the same kind, in the 'I'he present invention relates to automatic' stokers, and more particularly to automatic stokers for small boilers or heating plants in apartment houses or homes using either steam or hot water, but it may also be applicable to other and larger systems in the same manner as 'described herein.

Automatic stokers have been in use for a long time in large boiler plants of power houses, and in such systems the coal is usually passed over the lire by means of a grate formed as an endless chain which continually feeds the coal at the desired rate. Such methods of feed have been found to be impractical for small systems on account of the machinery involved and the necessary small size grate needed, and as a result, the system more generally employed is to feed the coal by forcing it to move over a. stationary grate.

Various types of feed for small stationary grates have been developed in the past few years, the more generally favoured being those in which the coal is fed up through the bottom of the grate and is not burned, although preheated, until it reaches the top exposed part of the grate. In properly designed boilers, the tubes to be heated can be situated right above the live coals, and since the fire does not extend deeply into the grate, the bulk of the fire will be right near the water which is being heated. In these systems, the coal after it is burned and is ash, falls over the sides of the top of the grate and is then picked up by some mechanism and automatically carried away.

In all the systems above described, air is usually-fed into the systems, and the coal is burned in accordance with a definite and adjustable amount of air. These systems, like oil burning systems, may be controlled by thermostat or pressurestat or amr other control systems to maintain a constant temperature.

'I'he present invgntion is a system of the type described above and has certain new features which provide a more eiicient and more improved system. y

In other systems, certain difficulty has been encountered in removing the ash, and special means had to be provided so that the ash beneath the grate 'could be frequently removed every week or two weeks. In the present system practically no ash or dust gathers beneath the grate, and what dust does, can be removed at the end of the season when the re is cleaned out. In other systems, I have also observed that coal gas is apt to be forced back through the coal feed system, and that, in order to prevent this, the coal box is usually made air tight. This I avoid in my system by the manner in which the air is fed into the system.

Further improvements will be found in my sysmanner in which the coal is fed; and also in the manner in which the ash is removed. Other improvements and advantages will be noted upon consideration of the description of the embodiment of the invention illustrated in the armexed drawing, in which Figure 1 shows a view of the apparatus looking from the front where the electric motor is situated; Figure 2 shows a side view of the apparatus of Figure 1 with the heater outlined at the extremeright; Figure \3 shows a top view of the end shown in front in Figure 1 with the coal hopper removed; Figure 4 shows a top view of the apparatusgof Figure 1 at the grate end; Figure 5 shows a side view of the detail shown in Figure 4; Figure 6 shows an enlarged View of the grate from the top; Figure 7 shows a section taken on the line A--A of Figure 6, and Figure 8 shows a development of a part section through the grate elements.

In Figure 1 the coal hopper is shown at 1. Mounted before the hopper as shown in Figure 1 is a base 66 on which is mounted a gear box 6 operated. from the motor 3 through the pulleys 4 and 5 and the belt 21. 'Ihe pulley 5 operates the reduction gear system in the box 6, which is filled with gear oil. A number of sizes of pulleys 4 and 5 may be provided to give different base' feeds for the system, but the system may also be controlled by other controls which form nopart of this invention. The reduction gear system in the box 6 drives a'slow speed gear to which the screws 24, 25, and bevel gear 26 mesh directly er indirectly so that the screw 24 moves to force the coal forward and 25 to withdraw the ash while 26 operates a second bevel gear 27 which drives the conduit 16 inclined upwards and rotating in the plate 64.' Over the plate 64 is positioned the gear 17 meshing the gear 18 which drives the screw 19 operating to raise the ash in the conduit 20. The coal is forced forward in the center conduit 35 entering the conduit at the bottom of the hopper in the opening 22. The ash is pushed back in the conduit 34 while the third portion of the casing 3l is used for the air. The air is drawn in at the side of the fan 7 which is driven directly by the motor 3. A moveable disc B'is provided over the air intake, so that the air volume may be controlled by adjustment of the hub 10 of the disc on the threaded shaft 9. 'I'he air proceeds along the part of the casing marked 63 and enters the grate around the chamber 54sur rounding the coal intake conduit as will be presently explained.

The coal is forced by the screw 24 along the conduit 35 to the grate. For this purpose the conduit 35 is joined at its end to elbow 70 through which the coal is forced upwards into the opening 59 at thevbottom of the grate. As indicated in Figure 7, the elbow is formed in three parts, a

lower half 50, an upper half 51 and a cap 7l. The lower half is cast with ears 60 and depression in the top edge to form with the top half slits 52 while the top half 51 has around the open part of the elbow similar slits 53, 53 formed with the cap 71. Both cap 71 and top half of elbow 51 have ears at the corners through which the bolt 61 passes holding all three elements together. The top element has a U shaped groove 55 in which the grate elements rest as will be explained. The slits are formed in the elbow 70vso that air from the chamber 54 may be forced through into the coal and exert a sufficient pressure at that point in the system to feed the air upwards to the burning coal. If the air was forced into the coals, only in the grate alone, there would be a tendency for the air to flow downward as well and carry back some gas with it into the hopper. By sending the air in from the bottom of the grate, the gas which is driven off from the heated coals with the air, is driven upwards over the live coals and burned instead of escaping backwards into the rooms.

From the open end of the elbow 70, the coal enters the grate which is of the circular conic shape with steep walls. The grate is formed of two sets of elements, a wide bar 48 and a narrow bar 49. The large bar 48 is somewhat convex as indicated in Figure 7 and has teeth at the edge projecting upwards as indicated vby 57 in Figure 8. The back of the bar has a center element 56 extending downward perpendicular to the surface of the bar. The small elements 49 rest on the edges of the bar at the teeth 57 and have a back element 58 similar to the element 56.

The bars 48 and 49 have end tongues which fit in the groove 55 of the top cap 71 of the elbow and also are cut at the top to have the elements 56, 58 and back edge of the bars 48 and 49 lay against the casing 44 of the grates. The casing for the grate is mounted ori the top of the chamber 54 as shown in Figure 7 and is made air tight or nearly so by asbestos between the flange 73 of the case and the top 43 of the chamber. These pieces may be held together by bolts or in any suitable way. The casing 44 is provided with an L shaped flange 45 to which a top rim 46 is bolted by screws 47 holding the bars 48 and 49 in place, and at the same time forming a seal so that no air can get out at the edges. This ordinarily is quite destructive for air coming through at this point causes intense heat at the rim and rusts the bolts in so that they cannot be removed.

As the coal is forced upwards in the grate it burns when it gets near the top and the new coal being fed from the center slowly forces the ash to the edge where it drops over in the nre box around the grate. The coal is supplied with air as has been explained by feed in the elbow 71 and it' is also fed around the grate between the teeth 57 in the bar 48. The air enters here from the inside of the casing 44 connecting to the chamber 54.

The removal of the ash forms a distinctive part of this invention. -The ash drops down around the sides of the grate filling up the nre box to the height of the endless chain 33. 'I'his chain is driven by a sprocket gear 32 from the bevel gear 41 which is driven by the bevel gear 40 at the end of the screw 25 in the conduit 34 'for removing the ash. The endless chain 33 carries a few plates 30 projecting outward which carries the ashover the opening 28 in the conduit 34. A bar 74 is provided to see that the ash dropping into the pocket 281s not too large.. This bar is positioned just outside the path of the plate 30, and if the piece of ash is too large, it is pushed aside and does not come over the hole 28. 'I'he chain 33 is mounted between the plate 42 and a cylindrical collar 36 formed with a ange 37. 'Ihe ange 37 extends in a projecting corner 29 over the sprocket gear 32 and is adjustable by means of the nut 38 in the slot 39. The collar 36 as shown in Figure 6 can be moved to the right as far as is necessary to get proper tension on the chain 33 and then set in place by tightening the nut 38 in the slot 39.

The ash carried along the conduit 34 by the screw 25 is hoisted by means of screw 19 moving in the conduit 20 driven as explained above.

'Ihe screw 19 raises the ash in the conduit to the outlet pipe 13 and the ash drops down by gravity in the barrel 1l. When the barrel 11 is filled the outlet is thereby blocked and the ash is carried up further to the outlet 14 which empties into the barrel 12. If both barrels are illled the ash is carried further up the conduit to the safety valve 15'which is a loosely hung door, and which allows the ash to fall out freely on the iloor or in. a pan, if it is there. i

An advantage of having the outlets successively higher in the conduit 20, is that the same height barrel may be used and the conduits 13 and 14 be made long enough to reach a standard barrel.

Having now described my invention, I claim:

1. In an automatic stoker of the kind described, a fire pot structure including an external enclosed casing having an inwardly extending ange at the top thereof, a base member having a vertically positioned groove positioned within said casing, a set of wide grate bars and a set of narrow grate bars, the bars of one set having teeth at the edge thereof over which the bars of the other set rest, the ends of the bars being shaped to fit the groove at the base and the flange at the top of the fire pot respectively.

2. In an automatic stoker of the kind described, a fire pot structure including a substantially cir- .cular base, a top supporting element having a larger circular supporting element than the base and two sets of grate bars having 4outwardly convex surfaces, one set of said grate bars being substantially wider than the other and both being tapered from one end to the other, one set having teeth on which the other set rests, both said bars being shaped to fit the top and bottom bases of the fire pot.

v 3. In an automatic stoker of the kind described, a nre pot structure including a substantially circular base, a top supporting element having a larger circular supporting element than the base and not less than two sets of grate bars having convex surfaces, one set of which is; substantially wider than the other and bothsets being tapered towards the bottom, one set having teeth extending forward from'the surface at the edge thereof and serving as a support' for the other set. y A

4. A nre pot structure having an underfed grate including a base element with an opening therein through which the fuel is fed, an upper supporting wall for thegrate bars, and two sets of grate bars having'substantially segmental shape with a convex/surface, one of said sets being substantially wider than the other, one set having teeth at the outer surface edges uponwhich the other set rests, said segments being shaped to fit and be supported by the supporting elements.

ovrLA Lamm., 

